The present disclosure relates to an organic light emitting diode (OLED) display device, and more particularly, to a top emission type OLED display device that that increases reliability.
An OLED display device is a self-luminous type display device, and thus does not require a backlight unit such as is required in a liquid crystal display (LCD) device. Also, an OLED display device can be manufactured in a lightweight slim profile and through a simple manufacturing process. Also, as an OLED display device only requires a low voltage driving, has high emission efficiency and a wide viewing angle. OLED devices are in the limelight as a next generation display device.
The OLED display device includes a thin film transistor (TFT) disposed on a substrate, an OLED device electrically connected to the TFT to emit light, and a sealing substrate for covering the OLED device.
OLED display devices can be categorized into a bottom emission type display devices and a top emission type display devices depending on a direction in which the light is emitted.
Since the top emission type display device emits light through a sealing substrate, it can have a large aperture ratio compared to a bottom emission type display device. Also, in a top emission type display device, an aperture ratio is not influenced by a driving device, so that a variety of driving devices can be designed.
However, in a top emission type display device, a patterned cathode electrode is formed for each pixel using a conductive material having a corrosion characteristic, and then an organic emission layer and an anode electrode are formed on the cathode electrode, so that the cathode electrode is easily corroded. Accordingly, the top emission type OLED display device has a limitation in that the reliability is reducing due to the corrosion of the cathode electrode.